/*
 * contrib/intarray/_int_gist.c
 */
#include "postgres.h"

#include <limits.h>

#include "access/gist.h"
#include "access/stratnum.h"

#include "_int.h"

#define GETENTRY(vec,pos) ((ArrayType *) DatumGetPointer((vec)->vector[(pos)].key))

/*
** GiST support methods
*/
PG_FUNCTION_INFO_V1(g_int_consistent);
PG_FUNCTION_INFO_V1(g_int_compress);
PG_FUNCTION_INFO_V1(g_int_decompress);
PG_FUNCTION_INFO_V1(g_int_penalty);
PG_FUNCTION_INFO_V1(g_int_picksplit);
PG_FUNCTION_INFO_V1(g_int_union);
PG_FUNCTION_INFO_V1(g_int_same);


/*
** The GiST Consistent method for _intments
** Should return false if for all data items x below entry,
** the predicate x op query == FALSE, where op is the oper
** corresponding to strategy in the pg_amop table.
*/
Datum
g_int_consistent(PG_FUNCTION_ARGS)
{
    GISTENTRY  *entry = (GISTENTRY *) PG_GETARG_POINTER(0);
    ArrayType  *query = PG_GETARG_ARRAYTYPE_P_COPY(1);
    StrategyNumber strategy = (StrategyNumber) PG_GETARG_UINT16(2);

    /* Oid        subtype = PG_GETARG_OID(3); */
    bool       *recheck = (bool *) PG_GETARG_POINTER(4);
    bool        retval;

    /* this is exact except for RTSameStrategyNumber */
    *recheck = (strategy == RTSameStrategyNumber);

    if (strategy == BooleanSearchStrategy)
    {
        retval = execconsistent((QUERYTYPE *) query,
                                (ArrayType *) DatumGetPointer(entry->key),
                                GIST_LEAF(entry));

        pfree(query);
        PG_RETURN_BOOL(retval);
    }

    /* sort query for fast search, key is already sorted */
    CHECKARRVALID(query);
    PREPAREARR(query);

    switch (strategy)
    {
        case RTOverlapStrategyNumber:
            retval = inner_int_overlap((ArrayType *) DatumGetPointer(entry->key),
                                       query);
            break;
        case RTSameStrategyNumber:
            if (GIST_LEAF(entry))
                DirectFunctionCall3(g_int_same,
                                    entry->key,
                                    PointerGetDatum(query),
                                    PointerGetDatum(&retval));
            else
                retval = inner_int_contains((ArrayType *) DatumGetPointer(entry->key),
                                            query);
            break;
        case RTContainsStrategyNumber:
        case RTOldContainsStrategyNumber:
            retval = inner_int_contains((ArrayType *) DatumGetPointer(entry->key),
                                        query);
            break;
        case RTContainedByStrategyNumber:
        case RTOldContainedByStrategyNumber:
            if (GIST_LEAF(entry))
                retval = inner_int_contains(query,
                                            (ArrayType *) DatumGetPointer(entry->key));
            else
                retval = inner_int_overlap((ArrayType *) DatumGetPointer(entry->key),
                                           query);
            break;
        default:
            retval = FALSE;
    }
    pfree(query);
    PG_RETURN_BOOL(retval);
}

Datum
g_int_union(PG_FUNCTION_ARGS)
{
    GistEntryVector *entryvec = (GistEntryVector *) PG_GETARG_POINTER(0);
    int           *size = (int *) PG_GETARG_POINTER(1);
    int32        i,
               *ptr;
    ArrayType  *res;
    int            totlen = 0;

    for (i = 0; i < entryvec->n; i++)
    {
        ArrayType  *ent = GETENTRY(entryvec, i);

        CHECKARRVALID(ent);
        totlen += ARRNELEMS(ent);
    }

    res = new_intArrayType(totlen);
    ptr = ARRPTR(res);

    for (i = 0; i < entryvec->n; i++)
    {
        ArrayType  *ent = GETENTRY(entryvec, i);
        int            nel;

        nel = ARRNELEMS(ent);
        memcpy(ptr, ARRPTR(ent), nel * sizeof(int32));
        ptr += nel;
    }

    QSORT(res, 1);
    res = _int_unique(res);
    *size = VARSIZE(res);
    PG_RETURN_POINTER(res);
}

/*
** GiST Compress and Decompress methods
*/
Datum
g_int_compress(PG_FUNCTION_ARGS)
{
    GISTENTRY  *entry = (GISTENTRY *) PG_GETARG_POINTER(0);
    GISTENTRY  *retval;
    ArrayType  *r;
    int            len;
    int           *dr;
    int            i,
                min,
                cand;

    if (entry->leafkey)
    {
        r = DatumGetArrayTypePCopy(entry->key);
        CHECKARRVALID(r);
        PREPAREARR(r);

        if (ARRNELEMS(r) >= 2 * MAXNUMRANGE)
            elog(NOTICE, "input array is too big (%d maximum allowed, %d current), use gist__intbig_ops opclass instead",
                 2 * MAXNUMRANGE - 1, ARRNELEMS(r));

        retval = palloc(sizeof(GISTENTRY));
        gistentryinit(*retval, PointerGetDatum(r),
                      entry->rel, entry->page, entry->offset, FALSE);

        PG_RETURN_POINTER(retval);
    }

    /*
     * leaf entries never compress one more time, only when entry->leafkey
     * ==true, so now we work only with internal keys
     */

    r = DatumGetArrayTypeP(entry->key);
    CHECKARRVALID(r);
    if (ARRISEMPTY(r))
    {
        if (r != (ArrayType *) DatumGetPointer(entry->key))
            pfree(r);
        PG_RETURN_POINTER(entry);
    }

    if ((len = ARRNELEMS(r)) >= 2 * MAXNUMRANGE)
    {                            /* compress */
        if (r == (ArrayType *) DatumGetPointer(entry->key))
            r = DatumGetArrayTypePCopy(entry->key);
        r = resize_intArrayType(r, 2 * (len));

        dr = ARRPTR(r);

        for (i = len - 1; i >= 0; i--)
            dr[2 * i] = dr[2 * i + 1] = dr[i];

        len *= 2;
        cand = 1;
        while (len > MAXNUMRANGE * 2)
        {
            min = INT_MAX;
            for (i = 2; i < len; i += 2)
                if (min > (dr[i] - dr[i - 1]))
                {
                    min = (dr[i] - dr[i - 1]);
                    cand = i;
                }
            memmove((void *) &dr[cand - 1], (void *) &dr[cand + 1], (len - cand - 1) * sizeof(int32));
            len -= 2;
        }
        r = resize_intArrayType(r, len);
        retval = palloc(sizeof(GISTENTRY));
        gistentryinit(*retval, PointerGetDatum(r),
                      entry->rel, entry->page, entry->offset, FALSE);
        PG_RETURN_POINTER(retval);
    }
    else
        PG_RETURN_POINTER(entry);
}

Datum
g_int_decompress(PG_FUNCTION_ARGS)
{
    GISTENTRY  *entry = (GISTENTRY *) PG_GETARG_POINTER(0);
    GISTENTRY  *retval;
    ArrayType  *r;
    int           *dr,
                lenr;
    ArrayType  *in;
    int            lenin;
    int           *din;
    int            i,
                j;

    in = DatumGetArrayTypeP(entry->key);

    CHECKARRVALID(in);
    if (ARRISEMPTY(in))
    {
        if (in != (ArrayType *) DatumGetPointer(entry->key))
        {
            retval = palloc(sizeof(GISTENTRY));
            gistentryinit(*retval, PointerGetDatum(in),
                          entry->rel, entry->page, entry->offset, FALSE);
            PG_RETURN_POINTER(retval);
        }

        PG_RETURN_POINTER(entry);
    }

    lenin = ARRNELEMS(in);

    if (lenin < 2 * MAXNUMRANGE)
    {                            /* not compressed value */
        if (in != (ArrayType *) DatumGetPointer(entry->key))
        {
            retval = palloc(sizeof(GISTENTRY));
            gistentryinit(*retval, PointerGetDatum(in),
                          entry->rel, entry->page, entry->offset, FALSE);

            PG_RETURN_POINTER(retval);
        }
        PG_RETURN_POINTER(entry);
    }

    din = ARRPTR(in);
    lenr = internal_size(din, lenin);

    r = new_intArrayType(lenr);
    dr = ARRPTR(r);

    for (i = 0; i < lenin; i += 2)
        for (j = din[i]; j <= din[i + 1]; j++)
            if ((!i) || *(dr - 1) != j)
                *dr++ = j;

    if (in != (ArrayType *) DatumGetPointer(entry->key))
        pfree(in);
    retval = palloc(sizeof(GISTENTRY));
    gistentryinit(*retval, PointerGetDatum(r),
                  entry->rel, entry->page, entry->offset, FALSE);

    PG_RETURN_POINTER(retval);
}

/*
** The GiST Penalty method for _intments
*/
Datum
g_int_penalty(PG_FUNCTION_ARGS)
{
    GISTENTRY  *origentry = (GISTENTRY *) PG_GETARG_POINTER(0);
    GISTENTRY  *newentry = (GISTENTRY *) PG_GETARG_POINTER(1);
    float       *result = (float *) PG_GETARG_POINTER(2);
    ArrayType  *ud;
    float        tmp1,
                tmp2;

    ud = inner_int_union((ArrayType *) DatumGetPointer(origentry->key),
                         (ArrayType *) DatumGetPointer(newentry->key));
    rt__int_size(ud, &tmp1);
    rt__int_size((ArrayType *) DatumGetPointer(origentry->key), &tmp2);
    *result = tmp1 - tmp2;
    pfree(ud);

    PG_RETURN_POINTER(result);
}



Datum
g_int_same(PG_FUNCTION_ARGS)
{
    ArrayType  *a = PG_GETARG_ARRAYTYPE_P(0);
    ArrayType  *b = PG_GETARG_ARRAYTYPE_P(1);
    bool       *result = (bool *) PG_GETARG_POINTER(2);
    int32        n = ARRNELEMS(a);
    int32       *da,
               *db;

    CHECKARRVALID(a);
    CHECKARRVALID(b);

    if (n != ARRNELEMS(b))
    {
        *result = false;
        PG_RETURN_POINTER(result);
    }
    *result = TRUE;
    da = ARRPTR(a);
    db = ARRPTR(b);
    while (n--)
    {
        if (*da++ != *db++)
        {
            *result = FALSE;
            break;
        }
    }

    PG_RETURN_POINTER(result);
}

/*****************************************************************
** Common GiST Method
*****************************************************************/

typedef struct
{
    OffsetNumber pos;
    float        cost;
} SPLITCOST;

static int
comparecost(const void *a, const void *b)
{
    if (((const SPLITCOST *) a)->cost == ((const SPLITCOST *) b)->cost)
        return 0;
    else
        return (((const SPLITCOST *) a)->cost > ((const SPLITCOST *) b)->cost) ? 1 : -1;
}

/*
** The GiST PickSplit method for _intments
** We use Guttman's poly time split algorithm
*/
Datum
g_int_picksplit(PG_FUNCTION_ARGS)
{
    GistEntryVector *entryvec = (GistEntryVector *) PG_GETARG_POINTER(0);
    GIST_SPLITVEC *v = (GIST_SPLITVEC *) PG_GETARG_POINTER(1);
    OffsetNumber i,
                j;
    ArrayType  *datum_alpha,
               *datum_beta;
    ArrayType  *datum_l,
               *datum_r;
    ArrayType  *union_d,
               *union_dl,
               *union_dr;
    ArrayType  *inter_d;
    bool        firsttime;
    float        size_alpha,
                size_beta,
                size_union,
                size_inter;
    float        size_waste,
                waste;
    float        size_l,
                size_r;
    int            nbytes;
    OffsetNumber seed_1 = 0,
                seed_2 = 0;
    OffsetNumber *left,
               *right;
    OffsetNumber maxoff;
    SPLITCOST  *costvector;

#ifdef GIST_DEBUG
    elog(DEBUG3, "--------picksplit %d", entryvec->n);
#endif

    maxoff = entryvec->n - 2;
    nbytes = (maxoff + 2) * sizeof(OffsetNumber);
    v->spl_left = (OffsetNumber *) palloc(nbytes);
    v->spl_right = (OffsetNumber *) palloc(nbytes);

    firsttime = true;
    waste = 0.0;
    for (i = FirstOffsetNumber; i < maxoff; i = OffsetNumberNext(i))
    {
        datum_alpha = GETENTRY(entryvec, i);
        for (j = OffsetNumberNext(i); j <= maxoff; j = OffsetNumberNext(j))
        {
            datum_beta = GETENTRY(entryvec, j);

            /* compute the wasted space by unioning these guys */
            /* size_waste = size_union - size_inter; */
            union_d = inner_int_union(datum_alpha, datum_beta);
            rt__int_size(union_d, &size_union);
            inter_d = inner_int_inter(datum_alpha, datum_beta);
            rt__int_size(inter_d, &size_inter);
            size_waste = size_union - size_inter;

            pfree(union_d);
            pfree(inter_d);

            /*
             * are these a more promising split that what we've already seen?
             */

            if (size_waste > waste || firsttime)
            {
                waste = size_waste;
                seed_1 = i;
                seed_2 = j;
                firsttime = false;
            }
        }
    }

    left = v->spl_left;
    v->spl_nleft = 0;
    right = v->spl_right;
    v->spl_nright = 0;
    if (seed_1 == 0 || seed_2 == 0)
    {
        seed_1 = 1;
        seed_2 = 2;
    }

    datum_alpha = GETENTRY(entryvec, seed_1);
    datum_l = copy_intArrayType(datum_alpha);
    rt__int_size(datum_l, &size_l);
    datum_beta = GETENTRY(entryvec, seed_2);
    datum_r = copy_intArrayType(datum_beta);
    rt__int_size(datum_r, &size_r);

    maxoff = OffsetNumberNext(maxoff);

    /*
     * sort entries
     */
    costvector = (SPLITCOST *) palloc(sizeof(SPLITCOST) * maxoff);
    for (i = FirstOffsetNumber; i <= maxoff; i = OffsetNumberNext(i))
    {
        costvector[i - 1].pos = i;
        datum_alpha = GETENTRY(entryvec, i);
        union_d = inner_int_union(datum_l, datum_alpha);
        rt__int_size(union_d, &size_alpha);
        pfree(union_d);
        union_d = inner_int_union(datum_r, datum_alpha);
        rt__int_size(union_d, &size_beta);
        pfree(union_d);
        costvector[i - 1].cost = Abs((size_alpha - size_l) - (size_beta - size_r));
    }
    qsort((void *) costvector, maxoff, sizeof(SPLITCOST), comparecost);

    /*
     * Now split up the regions between the two seeds.  An important property
     * of this split algorithm is that the split vector v has the indices of
     * items to be split in order in its left and right vectors.  We exploit
     * this property by doing a merge in the code that actually splits the
     * page.
     *
     * For efficiency, we also place the new index tuple in this loop. This is
     * handled at the very end, when we have placed all the existing tuples
     * and i == maxoff + 1.
     */


    for (j = 0; j < maxoff; j++)
    {
        i = costvector[j].pos;

        /*
         * If we've already decided where to place this item, just put it on
         * the right list.  Otherwise, we need to figure out which page needs
         * the least enlargement in order to store the item.
         */

        if (i == seed_1)
        {
            *left++ = i;
            v->spl_nleft++;
            continue;
        }
        else if (i == seed_2)
        {
            *right++ = i;
            v->spl_nright++;
            continue;
        }

        /* okay, which page needs least enlargement? */
        datum_alpha = GETENTRY(entryvec, i);
        union_dl = inner_int_union(datum_l, datum_alpha);
        union_dr = inner_int_union(datum_r, datum_alpha);
        rt__int_size(union_dl, &size_alpha);
        rt__int_size(union_dr, &size_beta);

        /* pick which page to add it to */
        if (size_alpha - size_l < size_beta - size_r + WISH_F(v->spl_nleft, v->spl_nright, 0.01))
        {
            pfree(datum_l);
            pfree(union_dr);
            datum_l = union_dl;
            size_l = size_alpha;
            *left++ = i;
            v->spl_nleft++;
        }
        else
        {
            pfree(datum_r);
            pfree(union_dl);
            datum_r = union_dr;
            size_r = size_beta;
            *right++ = i;
            v->spl_nright++;
        }
    }
    pfree(costvector);
    *right = *left = FirstOffsetNumber;

    v->spl_ldatum = PointerGetDatum(datum_l);
    v->spl_rdatum = PointerGetDatum(datum_r);

    PG_RETURN_POINTER(v);
}
